Around 28 million years ago, the largest shark to have ever lived on Earth roamed the seas, tearing apart large marine mammals such as whales and dolphins. Measuring up to 18 meters in length, armed with teeth up to 7 inches long, the iconic Carcharocles megalodon (“Megalodon”) was a formidable predator.
Although it has been widely regarded as extinct by the scientific community due to a lack of sightings and recent specimens, a mockumentary by the Discovery Channel perpetuated the idea that this apex predator could still be lurking deep in the ocean, avoiding detection by scientists. And of course, absence of evidence is not necessarily evidence of absence. But now, a comprehensive new study by researchers at the University of Florida and the University of Zurich has suggested that this ferocious vertebrate became extinct some 2.6 million years ago, rejecting popular ideas that Megalodon still survives today. The work has been published in PLOS ONE.
Megalodon fossils, in particular teeth, have been unearthed in a considerable number of places across the globe, suggesting that this animal was a cosmopolitan fish that inhabited a wide range of marine environments. These fossils generally range from the middle Miocene (15.9-11.6 million years ago [Ma]) to the Pliocene (5.3-2.6 Ma). Despite the abundance of fossils, surprisingly, little was known about the extinction of Megalodon. Researchers are particularly interested in the extinction of apex predators because of the downstream effects on the food chain that can be triggered, but working out when these events likely occurred can be tricky due to incomplete fossil records.
To gain a better understanding of the extinction of this animal, researchers sifted through the Paleobiology Database to identify the most recent Megalodon fossils and found a total of 53. Of these records, 42 were considered reliable, so only these were included in the analysis. The age of these specimens lies within a range of an upper and lower date estimate, so to account for this uncertainty they ran 10,000 simulations for each fossil. This then selected the most likely age between these boundaries.
They then applied a technique called optimal linear estimation to infer when Megalodon became extinct. This involves examining the distribution of gaps between fossil dates through time, study author Chris Clements told Live Science. Although it can’t give a specific date for when the animal became extinct, it provides the most statistically likely extinction date, he said.
According to the calculations, Megalodon became extinct around 2.6 Ma and is unlikely to have survived after this date. Six of the simulations actually inferred an extinction date after the present day, which would mean that it cannot be considered extinct. But because over 99.9% of the simulations gave a date in the past, the team rejected the hypothesis that Megalodon survives today. Hopefully, this will help dispel the popular myth that Megalodon is still skulking somewhere in our oceans.
Interestingly, the inferred date of extinction fell around the same time that modern, gigantic filter-feeding whales became established, suggesting that the disappearance of Megalodon may have contributed to the evolution of these animals. Future studies will examine this further.
[Via PLOS ONE, Live Science and University of Florida]